The embodiments described herein relate generally to wind turbines and, more particularly to a system and method for controlling a wind turbine.
At least some known wind turbines include a nacelle fixed on a tower. The nacelle includes a rotor assembly coupled to a generator through a shaft. In known rotor assemblies, a plurality of rotor blades extend from a rotor. The rotor blades are oriented such that wind passing over the rotor blades turns the rotor and rotates the shaft, thereby driving the generator to generate electricity.
During operation of known wind turbines, power output generally increases with wind speed until a rated power output is reached. At least some known wind turbines adjust a pitch of the rotor blades in response to an increase in wind speed to maintain a constant power output. At least some known wind turbines includes a feedback control system to monitor the wind turbine power output and to change a pitch of a rotor blade pitch to adjust the power output to a predefined power output level.
In case of sudden turbulent gusts, wind speed, wind turbulence, and wind shear may change drastically in a relatively small interval of time and may cause rotor imbalance. At least some known wind turbines have a time lag between the occurrence of a turbulent gust and the pitching of the rotor blades based on the operation of the feedback control system. As a result, load imbalances and generator speed may increase significantly during such turbulent gusts, and may exceed the maximum predefined power output level that cause the generator to trip and the wind turbine to shut down. In addition, the rotor blades may be subjected to stresses that cause fatigue cracking and/or failure, which may eventually cause suboptimal performance of the wind turbine.